JPS6359548A - Manufacture of thermal head - Google Patents

Abstract

PURPOSE:To shorten the period of time required to form a table, by fixingly providing a value of an applied voltage at which a change in resistance appears, in determining a voltage of a voltage pulse to be applied by using a resistance vs. applied voltage table. CONSTITUTION:The resistance change ratio of a resistor capable of being approximated by the equation based on measurements for selected samples of dots in a thermal head varies substantially along a fixed curve, irrespective of the initial resistance of the resistor. In the equation, R0 is the initial resistance of a heat generating resistor, V0 is a boundary value of applied voltage at which a change in resistance appears, DELTAV is the change in resistance, and alphaand beta are constants. The boundary values V0 of applied voltage are centralized at about 25V. The resistance change ratio DELTAR=(R-R0)/R0 is put into the equation, with the boundary voltage V0 given as a fixed value of 25V, whereby a solution can be speedily obtained. Specific values DELTARn of the resistance change ratio are sequentially put into the equation to calculate the values of the applied voltage at a given moment, thereby forming a resistance vs. applied voltage table. A voltage Vn to be applied is determined based on the table.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a thick film thermal head, and particularly to making the resistance value of a heating resistor thereof uniform.

[Conventional technology]

In the thick film type thermal head, a heat generating resistor is formed by printing a paste-like resistive material into a predetermined pattern by screen printing or the like, and then firing it. Therefore, although the thick film type thermal head can be manufactured at low cost through a relatively short manufacturing process, it has the disadvantage that the resistance value of the heating resistor varies widely. Variations in the resistance value of the heating resistor directly affect the quality of printing, so uniformity of the resistance value of the heating resistor is an extremely important factor in the manufacture of thick-film thermal heads. . To make the resistance values of the heating resistors uniform, there is a trimming process that utilizes the phenomenon that after the heating resistors are formed, when a relatively high voltage pulse is applied to each heating resistor individually, the resistance value decreases. .

FIG. 5 is a flowchart showing a conventional thermal head manufacturing method disclosed in, for example, Japanese Unexamined Patent Publication No. 61-83053. In FIG.
Sr1 is a prober and switching step following step ST1, Sr1 is a voltage pulse application step following step ST2, and Sr1 is step ST
Sr1 is a step of comparing with the previous data following step ST4, Sr6 is a step of detecting a decrease in resistance value following step ST5,
Sr1 is a step for detecting the end of all trimming dots following step ST6, Sr8 is a step branching from step ST5 or a probe step, Sr1 is a step for voltage adjustment of voltage pulses branching from step ST6, and step ST7 is From the branch of step ST
2, from step ST8 to step ST4, and from step ST9 to step ST3.

Next, the operation will be explained. First, in step ST1, initial conditions such as the initial value of the voltage pulse applied to the heating resistor to be trimmed and the target value for trimming are set.Next, in step ST2, the thermal head is probed and a dot to be trimmed is selected. Then connect the heating resistor to voltage pulse generating means, and step ST
In step 3, a voltage pulse having the initial value set in step 1 is applied.Next, in step ST4, the resistance value of the heating resistor is measured, and in step ST5, it is determined whether or not the resistance value has decreased. If not, it is assumed that the contact of the probe is poor and the probing is repeated in step ST8.
Return to step ST4 and measure the resistance value again. If the resistance value has decreased, proceed to step ST6 and measure the resistance value again.
Compare with the trimming target value set in I, and if it is not smaller than the target value, increase the voltage value of the voltage pulse by ΔV in step ST9, return to step ST3, and reapply the voltage pulse. This process is repeated until the resistance value of the heating resistor becomes smaller than the target value, and when the resistance value of the heating resistor becomes smaller than the target value, the trimming of the heating resistor of the dot is completed and the process moves to step ST7. In step ST7, it is determined whether or not all dots have been trimmed. If all dots have not been trimmed, the process returns to step ST2. In step ST2, a new dot is selected and its heating resistor is is connected to the voltage pulse generating means, and the same process is repeated until all dots are trimmed.

Figure 6 is a diagram showing the decrease in the resistance value of this heating resistor. Before trimming, the resistance value varied widely as R, , R, , R, but now it is slightly lower than the target value R0, and is narrower. In the figure, v5 is the initial value of the voltage pulse, which is set to 25V, for example, because the boundary voltage at which the resistance value of the heating resistor starts to decrease by application of the voltage pulse is usually around 25V. ing. Also, ΔV
is the increment in the voltage value of the voltage pulse in step ST9, and is set to, for example, 2.5 V so that the resistance value of the heating resistor 9 does not decrease too much, and the resistance value is gradually decreased.

[Problem that the invention seeks to solve]

Since the conventional thermal head manufacturing method is configured as described above, it takes two steps to trim one dot of the heating resistor.
There is a problem in that it is necessary to apply a voltage pulse 0 to 30 times and measure the resistance value, and it takes a lot of time to equalize the resistance value of the heating resistor.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing a thermal head that does not require a large amount of time to equalize the resistance value of the heating resistor. do.

[Means for solving problems]

The method for manufacturing a thermal head according to the present invention involves selecting several samples from among the dots of the thermal head, applying several voltage pulses with different voltage values to the samples in order from the lowest to the lowest, and measuring the resistance of the heating resistor each time. When a change in resistance value begins to appear, a resistance vs. applied voltage table is created by fixing the representative value as the boundary value of the applied voltage. The resistance value of the resistor is measured, and the voltage value of the voltage pulse to be applied is determined from the required amount of drop in resistance value using the resistance vs. applied voltage table.

[Effect]

A method of manufacturing a thermal head according to the present invention is as follows.

Measure the sample dot in the thermal head,
By creating a resistance vs. applied voltage table by giving a fixed representative value in advance to the boundary value of the applied voltage at which a change in resistance value begins to appear, the creation time can be shortened. Using the voltage table,
The voltage value of the voltage pulse to be applied is determined from the measured resistance value of the heating resistor of that dot, and the resistance value of the heating resistor is brought close to the target value by applying one voltage pulse.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, STI 1 is the initial setting step, 5T1
2 is the step of measuring the resistance change of the sample following step 5TII, 5T13 is the step of creating a resistance vs. applied voltage table following step STI 2, 5T14 is the step of measuring the resistance value following step 5T13, 5
T15 is a step of determining the applied voltage following step 5T14, 5T16 is a voltage pulse application step following step 5T15, and 5T17 is step 5T16.
This is the step of detecting the end of all the trimming dots following step 5T17, and from step 5T17 branching to step 5T14.
Processing is returned to .

FIG. 2 is a block diagram showing an example of an apparatus for carrying out the method of manufacturing a thermal head of the present invention, and in the figure, 1
2 is a thermal head where trimming processing is performed; 2 is a blowing device that presses a probe against the terminal of each heating resistor of this thermal head 1; 3 is a blowing device W1;
2 is a relay network connected to select the heating resistor; 4 is a switch connected to relay network 3 and switches between applying voltage pulses and measuring resistance; 5 is a switch connected to one side of switch 4 for designation; 6 is a resistance meter connected to the other side of the switch 4; 7 is an input/output unit 8; a central processing unit (hereinafter referred to as CPU) 9; a memory 10; a keyboard 11; 12 is a printer connected to this control calculation section 7.

Next, the operation will be explained. FIG. 3 is a diagram showing an example of the resistance value drop curve, and the solid line Y in the figure is the resistance value drop curve, and the horizontal axis shows the applied voltage value due to the voltage pulse.
On the vertical axis, the rate of change in resistance of the heating resistor due to voltage pulse application is scaled.

As a result of the experiment, when we plot the percentage drop from the initial resistance value with the vertical axis in Figure 6 as the resistance change rate, we find that it remains almost constant regardless of the initial resistance value, as shown by the broken line in Figure 3. It turns out that the curve Y can be approximated by equation (1).

Ro ΔV In formula (1), Ro is the initial resistance value of the heating resistor,
(2) is the boundary value of the applied voltage at which a change in resistance value begins to appear, ΔV is the change step of the applied voltage, and α and β are constants determined by the structure of the thermal head, dot density, etc.

In addition, as a result of another experiment, a voltage pulse of a predetermined voltage value was
The resistance reduction rate when the voltage pulse is applied only once is equivalent to that of the same voltage value when the voltage pulse is applied many times while increasing the voltage value as shown in Figure 3, and furthermore, the resistance value Boundary voltage value v0 of the applied voltage at which a change begins to appear
varies depending on the individual thermal head,
It was also found that the values were concentrated around 25V, and there was no large variation. This invention is based on these experimental results.

In this embodiment, first, initial settings are performed in step 11, and then, in step 12, resistance change measurement of the sample is performed. That is, the relay network 3 is controlled to select a designated dot heating resistor as a sample of the thermal head 1, and the switch 4 is switched to connect it to the resistance meter 6 to measure the resistance value.

The measured value is sent to the control calculation unit 7, and the CP of the control calculation unit 7 is
U9 stores this in the memory 10, and then switches the switch 4 to apply a voltage pulse of a predetermined voltage value from the pulse generator 5 to the resistance heating element. Here, this voltage pulse includes, for example, 15 pulses each having a width of 2 μsec and a period of 50 μsec.
Next, turn switch 4 again, which is a pulse train that continues in seconds.

The heating resistor to which this voltage pulse has been applied is connected to a resistance meter 6 to measure the resistance value and send it to the control calculation section 7. The CPU 9 of the control calculation section 7 stores it in the memory 10 together with the voltage value of the applied voltage pulse.

Thereafter, these processes are repeated in the same manner while appropriately increasing the voltage value of the voltage pulse. This process is repeated at least three times, and is executed for several samples by switching the relay network 3.

Next, in step 5TI3, the resistance value drop curve is approximated based on the resistance change measured in this manner. That is, the CPU 9 of the control calculation unit 7 calculates the resistance change rate ΔR= (R-R@)/ at each applied voltage due to the voltage pulse from the resistance change stored in the memory 10.
Find R@ and substitute it into the equation (1) above. At this time, the boundary voltage V at which a change in resistance value begins to appear is as follows:
A typical value thereof, for example 25V, is fixedly given. From this, we create and solve equations with α and β as unknowns for each sample, here.

When there are three or more equations for two unknowns, they are processed using statistical means to obtain a solution. This equation is α
, βt V6 as unknowns, the solution can be obtained in a much shorter time, and the solution also has a boundary voltage value V of 25
Since it is concentrated near V, it does not contain large errors.The obtained solution is further statistically processed between each sample.

The obtained constants α and β are substituted into equation (1), and a resistance drop curve in which the origin moves to the position indicated by the two-dot chain line in FIG. 3 is approximated, and the resistance change rate ΔR and the applied voltage V are Next, calculate the value of the applied voltage Vn at that time by sequentially subtracting the specific value ΔRn of the resistance change rate into the obtained equation, and then arrange the two in correspondence. Create a resistance vs. applied voltage table. FIG. 4 is an explanatory diagram showing an example of this resistance versus applied voltage table.

This completes the preparation stage and starts the trimming process from step 5T14. First, in step 5T14,
The relay network 3 selects the dot to be trimmed, and the switch connects it to the resistance meter 6 to measure its resistance value.In step 5T15, the CPU 9 lowers the obtained resistance value to the target value. The rate of resistance change ΔRn to
The applied voltage Vn corresponding to Rn is read to determine the applied voltage of the voltage pulse. in particular.

For example, the resistance versus applied voltage table is read by a binary search method (intermediate comparison method) or the like.

For intermediate values of the resistance change rate ΔRn in the table, the applied voltage is determined by proportional allocation or the like. Alternatively, the read applied voltage Vn may be used as is.

The obtained applied voltage is sent from the control calculation section 7 to the pulse generator 5. When the switch 4 is switched in step 5T16, a voltage pulse whose voltage is adjusted to the applied voltage is sent out from the pulse generator 5, and is applied to the heating resistor of the dot to be trimmed. As a result, the resistance value of the heating resistor falls to a value close to the target value. Thereafter, the processing from step 5T14 onward is repeated until step 5T17 detects that all dots have been trimmed.

Further, in the above embodiment, a predetermined number of continuous pulse trains are used as the voltage pulse, but a single pulse may be used, and the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the origin is moved by measuring the resistance change of a small number of samples and fixedly giving a representative value to the boundary voltage value at which the resistance value starts to change. A resistance vs. applied voltage table was created, and during trimming, the resistance value of the heating resistor of the dot was measured, and the voltage value of the voltage pulse was determined using the resistance sealed applied voltage table. A resistance vs. applied voltage table can be created in a short time, trimming can be completed by applying one voltage pulse to each dot, and the voltage value of the voltage pulse can be determined without the need for troublesome calculations. This can be done in a short amount of time, and has the effect of significantly reducing the time required to equalize the resistance values of the heating resistors.

This effect is similar to that of a thermal head for facsimile.

This is particularly noticeable when applied to a multi-dot thermal head having a heating resistor of 1000 dots or more.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a method for manufacturing a thermal head according to an embodiment of the present invention, FIG. 2 is a block diagram showing an example of an apparatus for carrying out the method, and FIG. 3 is an example of a resistance value drop curve. Fig. 4 is an explanatory diagram showing an example of the resistance sealed applied voltage table, Fig. 5 is a broach yard showing a conventional method of manufacturing a thermal head, and Fig. 6 is a diagram showing a reduction in the resistance value of the heating resistor. FIG. 1 is a thermal head, 2 is a blobbing device. 3 is a relay network, 4 is a switch, 5 is a pulse generator, 6 is a resistance meter, and 7 is a control calculation section. Patent applicant: Mitsubishi Electric Corporation Figure 1 Figure 2 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In a method for manufacturing a thermal head, in which a voltage pulse is applied to each of the heating resistors of a thermal head including a plurality of heating resistors to lower and equalize the resistance value, the voltage at which the resistance value starts to drop; A representative value is fixedly given in advance as the boundary value of the applied voltage of the pulse, and a sample is selected from the heat generating resistor, and voltage pulses with different voltage values are sequentially applied from the lowest to the lowest as the sample. Create a resistance vs. applied voltage table that shows the relationship between the applied voltage and resistance change by applying it to the selected heating resistor, and set the voltage value of the voltage pulse applied to each heating element to the initial value of the heating resistor. A method for manufacturing a thermal head, characterized in that the determination is made using the resistance vs. applied voltage table based on the resistance value of .